It is known that a number of fuel cells are joined together to form a fuel cell stack. Such a stack generally provides electrical current in response to electrochemically converting hydrogen and oxygen into water. The electrical current generated in such a process is used to drive various devices in a vehicle or other such apparatus. A supply generally provides hydrogen to the fuel cell stack. The fuel cell stack may use less hydrogen than provided by the supply to generate electrical power. An ejector receives unused hydrogen discharged from the fuel cell stack and combines the unused hydrogen with the hydrogen generated from the supply to sustain a flow of hydrogen to the fuel cell stack.
During fuel cell operation, byproducts such as product water and nitrogen, and unconsumed hydrogen may form at the anode side of a fuel cell stack. Liquid water, such as droplets, or water vapor may need to be removed to prevent water blockages within fuel cell stack flow field channels or an ejector.
For a fuel cell application in a vehicle, the fuel cell may be required to operate in freezing ambient temperatures. The vehicle and fuel cell may be exposed to temperatures of −25 Celsius or even lower, well below the freezing point for water. Cold weather operating issues need to be addressed for a fuel cell vehicle to operate in climates with extreme ambient temperatures, and to meet user expectations for the vehicle. When exposed to freezing conditions, any water found within the fuel cell system may freeze, forming ice blockages that may prevent reactant or byproduct flow and result in delayed or unsuccessful fuel cell system start ups or a reduction in operating performance.
In some prior art systems, water is removed from the fuel cell system at system shut down to prevent the water from freezing if the fuel cell system is exposed to freezing conditions. Prior art systems may use high pressure air to remove water from the stack membrane after system shut down. Other prior art systems may heat the system to remove liquid water via evaporation and dry the system; however, this may be energy intensive and reduce efficiencies. Prior art systems may also have an on-board monitor to wake up the fuel cell system after system shut down and conduct a pressurized-air blow out or enable a heating process if ambient temperatures go below a threshold.